Multilayer board for reducing solid-borne sound

ABSTRACT

A multilayer board for reducing solid-borne sound radiation with improved mechanical stability when subjected to a load, comprising a first cover layer, a second cover layer, and at least one core layer, wherein the at least one core layer is arranged between the first and the second cover layer, and wherein the at least one core layer comprises at least one first sloped slot.

REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of the filing date of German PatentApplication No. 10 2007 022 616.2 filed May 15, 2007 and of U.S.Provisional Patent Application No. 60/930,440 filed May 15, 2007, thedisclosures of which applications are hereby incorporated herein byreference.

FIELD OF THE INVENTION

The present invention relates to a multilayer board, a means oftransport comprising at least one multilayer board according to theinvention, and the use of a multilayer board according to the inventionin a means of transport.

TECHNOLOGICAL BACKGROUND OF THE INVENTION

In conventional multilayer boards for reducing solid-borne sound themain design aim has been as effective as possible a reduction in soundradiation, as can be found, for example, in DE 100 34 990 B4. Saidprinted publication discloses the design of a multilayer board thatessentially comprises three layers, wherein the middle layer is slottedroughly in a cross-shape. However, as a result of the relatively largeslots, it may be possible that there is not only a reduction insolid-borne sound radiation but also in the mechanical stability whensubjected to a load.

SUMMARY OF THE INVENTION

It may be desirable to have a multilayer board for reducing solid-bornesound radiation, which multilayer board provides improved mechanicalstability when subjected to a load.

According to an exemplary embodiment of the present invention, amultilayer board for reducing solid-borne sound radiation is created,which multilayer board provides improved mechanical stability whensubjected to a load, wherein the multilayer board comprises a firstcover layer, a second cover layer and at least one core layer, whereinthe at least one core layer is arranged between the first and the secondcover layer, and wherein the at least one core layer comprises at leastone first sloped slot.

In the context of the present patent application the followingdefinitions are used:

-   Slot: The term “slot” refers to any elongated or essentially    area-shaped recess in a material, in the present context in    particular in the core layer of the multilayer board, wherein the    slot preferably extends from a surface into the material. In this    arrangement the slot can be made with the use of various processing    methods, for example, but not exhaustively, by sawing, filing,    milling, drilling, etching and the like. The hollow space created in    this manner may be left as such or it may be filled with a material,    e.g. a foam, plastic or some other-   Sloped slot: The term “sloped slot” refers to a slot, in particular    arranged in a core layer of a multilayer board, which slot in    relation to the normal on the surface on which the slot is formed    does not extend parallel but instead at an angle into the core    layer, and furthermore at least in sections extends in one of the    principal directions of extension of the core layer. Thus an angle μ    forms between the normal on the surface of the core layer and the    direction of transverse extension of the sloped slot, which angle μ    differs from 0°.-   Direction of longitudinal extension: In its idealised    two-dimensional extension the slot or sloped slot according to the    invention comprises essentially two different principal directions    of extension. In this arrangement that principal direction of    extension which extends so as to be essentially parallel to the    surface of core layer(s) or to the first and/or second cover layer    is designated the direction of longitudinal extension. For example    in the case of a curved or partly linear course of the sloped slot,    this direction of longitudinal extension may be defined also only in    sections or by way of the tangent of the curvature at a given point    of the sloped slot.-   Direction of transverse extension: In the context of the present    invention the direction of transverse extension is regarded as the    second principal direction of extension. The direction of transverse    extension extends into the thickness of the core layer at an angle    to the surface normal of the core layer. In the case, for example,    of a curved or partly linear course of the sloped slot, the    direction of transverse extension, too, may only be defined in    sections or by way of the tangent of the curvature at a given point    of the sloped slot. In this arrangement, the direction of    longitudinal extension and the direction of transverse extension may    be aligned so as to be perpendicular in relation to each other.

The present invention describes multilayer boards as they may amongother things be used in aircraft construction for interior paneling ofthe passenger cabin. In this application, apart from the aesthetic,visual aspect, the aspects of sound absorption and reduced solid-bornesound radiation may also play a significant role. The multilayer boardaccording to the invention may thus, for example, be used as paneling onthe inside of the covering or as a kind of space divider that isarranged so as to be essentially perpendicular to the longitudinal axisof the aircraft (e.g. between different seating categories, or topartition-off galleys, rest areas, sanitary installations etc.). In theformer application the multilayer board according to the invention may,among other things, suppress sound propagation in the cabin as a resultof reflection on the partition walls, or may acoustically separate thelines, for example air lines and pneumatic lines, that are situatedbehind the paneling, i.e. between the aircraft envelope and themultilayer board, from the passenger cabin, and also from air thatenters the aircraft envelope from the outside.

Below, the acoustic behaviour of multilayer boards is briefly set out.

Accordingly, in the low frequency range the occurrence of lateralflexural waves is observed whose speed is determined by the overallflexural strength of the multilayer board. As the frequency increases,the flexural wave starts to slowly make a transition to a lateral shearwave, whose propagation speed increases proportionally to the root ofthe core-layer shear modulus, irrespective of the frequency. At stillhigher frequencies the lateral shear wave then makes a transition to alateral flexural wave, whose propagation speed is determined by theflexural strength of the cover layers of the multilayer board. If therewere a possibility, in this situation, to be able to select the shearmodulus of the core layer in a suitable manner, it may be possible toachieve a situation in which the lateral waves in the entire frequencyrange of interest remain below the speed of sound in air. Bycorresponding manipulation of the parameters of cover layer thickness,core layer thickness, cover layer-E-module, and density of the coverlayers and the core layer, a situation can be achieved wherein themultilayer board has an advantageous acoustic behaviour. At the sametime the flexural strength of the multilayer board considered may bekept sufficiently high in the non-loaded state.

Thus, in order to obtain a multilayer board that is advantageouslydesigned from an acoustic point of view, corresponding measures may haveto be provided which in view of the above considerations aim to reducethe core-layer shear rigidity of the multilayer board according to theinvention, which core-layer shear rigidity is physically directlyproportional to the core-layer shear modulus. The reduction in thiscore-layer shear rigidity may be achieved by a suitable slot arrangementof the core layer of the multilayer board according to the invention.

However, known slot arrangements of the core layer of the multilayerboard may be at the same time associated with a reduction in mechanicalstability. Since corresponding multilayer boards are essentially placedin the passenger cabin of an aircraft, and are thus subjected to directcontact with passengers, a corresponding exposure to loads is afrequently-occurring case. This ranges from passengers simply supportingthemselves when leaving the passenger seat or resting against saidmultilayer boards when they are tired during a flight. However, inextreme cases corresponding multilayer boards also have to withstandbrief but possibly very violent impact loads, at times restricted tosmall areas, for example if a passenger falls against a correspondingmultilayer board, or if a service trolley that is more or less out ofcontrol crashes against said multilayer board. In a conventional designof a multilayer board it is possible, by way of slots that in a targetedmanner have been introduced into the core layer for improving theacoustic characteristics, for a corresponding force to cause extensivedeformation which to a very considerable extent subjects the individualcomponents of the multilayer board to tensile/shear stress.

By designing the multilayer board according to the invention withrelatively small sloped slots, a design may be achieved which on the onehand provides an acoustically favourable design, and on the other hand,when subjected to external force, permits only little deformation andassociated tensile/shear stress or shear forces. This may be achieved bymeans of a sloped-slot design in which the sloped slots when subjectedto forces essentially close up immediately, with the result being anessentially compact coherent or continuous core layer with a behaviourthat is similar to a solid non-slotted core layer.

Multilayer boards according to the invention may be made from aplurality of suitable materials, e.g. plastic, metal or fibre-reinforcedmaterials comprising carbon-, glass- or aramide fibres. The individualcomponents of the multilayer board may comprise different or identicalmaterials. In this process the selection of materials takes place takinginto account the inventive idea. In this context, foams are materials,which may be particularly advantageous.

Further exemplary embodiments are stated in the dependent claims.

Furthermore, embodiments of the multilayer board according to theinvention are described. However, these explanations apply both to themeans of transport comprising at least one multilayer board, and to theuse of a multilayer board in a means of transport.

According to an exemplary embodiment of the present invention, the atleast one first sloped slot on a first side of the at least one corelayer may be open, and on the second side, which is arranged oppositethis first side it may be not open. In this context the term “open”refers to reaching through the surface or the material. The second side,which is opposite said first side, may be not open, i.e. designed sothat it does not reach through the material. In this way the slot designmay in a simple manner be incorporated in the material of the core layerwithout reducing or exceeding the stability or structural integrity ofthe core layer to such an extent that simple handling or installation ofthe processed/prepared core layer is no longer possible. However, adesign may also be imaginable in which the first sloped slot reachesthrough the surface on both sides. In this case the stability or theintegrity may be ensured by at least one of the cover layers.

According to another exemplary embodiment of the present invention, theat least one core layer furthermore may comprise at least one secondsloped slot, wherein the at least one first sloped slot and the at leastone second sloped slot within the surface with their respectivedirection of longitudinal extension parallel to the surface of the atleast one core layer may comprise an angle α.

According to another exemplary embodiment of the present invention, theangle α may essentially be 90°. Consequently, the direction oflongitudinal extension of the at least one first sloped slot and the atleast one second sloped slot may be arranged so as to be essentiallyperpendicular to each other, thus essentially forming a rectangularpattern. However, any other angles are of course also imaginable, e.g.45°, 30°, 60°, 22.5°, 67.5°. In principle any angle ranging between 0and 90° may be possible, wherein for the sake of simplicity always anacute enclosed angle is considered. However, it may also be possible forthe direction of longitudinal extension of the sloped slots to locallychange relative to the surface of the core layer, without the enclosedangle α changing. This may result in an even change in the directionsfrom the first and second sloped slots, without however there being achange a of the angle enclosed by the respective local directions.

According to another exemplary embodiment of the present invention, theangle α may dynamically change with the course of the at least one firstsloped slot and the at least one second sloped slot. As described above,the respective directions of longitudinal extension of the first andsecond sloped slots relative to the core layer may change with thecourse of the sloped slots. In this arrangement these changes may alsobe independent of each other so that this results in a dynamic change inthe respective local angle α.

According to another exemplary embodiment of the present invention, thefirst sloped slot may be a sloped slot selected from the groupcomprising a single sloped slot, double sloped slot, multiple slopedslot, fan-shaped sloped slot and a Y-shaped sloped slot. In thisarrangement this geometric design may remain the same over the entirelength of the slot or it may change in sections and/or intervals.Sectional transitions, so-called morphing-transitions, between twogeometric embodiments may also be imaginable.

According to another exemplary embodiment of the present invention, themultilayer board may comprise a multitude of core layers. In this waystill further-reaching design options may result. The materials of theindividual core layers may be the same or they may differ from eachother. The slot design and/or its principal directions of extension maybe the same or they may differ. It may also be possible to design andarrange the respective sloped slots of the individual core layers suchthat an advantageous transition according to the invention is formedbetween them. In this arrangement the slots may overlap entirely or inpart and may, at least in some regions, be arranged so that theiropenings point away from each other (in other words in each case twoopenings followed by two non-openings facing each other).

According to another exemplary embodiment of the present invention, theconnection between the cover layer and the core layer, as well as theconnection between two core layers, may at least in some regions bedesigned as a connection from the group comprising an adhesiveconnection, solder connection, weld connection, press connection and amixture of the aforementioned.

According to another exemplary embodiment of the present invention, asloped slot may be designed such that when an external force acts on themultilayer board, the at least one sloped slot is essentially beingclosed from a particular limiting force onward. In this arrangement thesloped slots may be dimensioned such that in the case of point-shaped orlarge-area force that acts temporarily or over an extended period oftime, said sloped slots close as a result of mechanical deformation orbending of the multilayer board. In this way a compact and essentiallycontinuous core layer and thus a multilayer board may be created again.Smaller, non-closed slot regions, for example in the region ofattachment of the core layer to a cover layer, can be disregarded inthis context. The success according to the invention, of the presentinvention, may nevertheless be realised in this arrangement. In thisarrangement, corresponding closing-off may take place quasi directly, inother words without extensive deformation of the multilayer board.

According to another exemplary embodiment of the present invention, ameans of transport may comprise at least one multilayer board. In thisarrangement, the term “means of transport” may refer to any vehicle thatconveys either persons or goods either commercially or non-commercially.This includes buses, rail vehicles, motor vehicles, ships and boats, andin particular also aircraft.

According to another exemplary embodiment of the present invention, amultilayer board according to the invention may be used in a means oftransport.

Below, exemplary embodiments of the invention, which are, however, notto be interpreted as limiting, are shown in the following figures andare explained in more detail.

SHORT DESCRIPTION OF THE DRAWINGS

The following are shown:

FIG. 1 a perspective view of a multilayer board according to anexemplary embodiment of the invention, comprising a slot design as asimple sloped slot.

FIG. 2 a perspective view of a multilayer board according to anotherexemplary embodiment of the invention, comprising a slot design as adouble sloped slot.

FIG. 3 a,b section views of a multilayer board according to anotherexemplary embodiment of the invention in a deformed state when subjectedto external loads, and in a non-deformed state.

FIG. 4 a-e profile sections of various sloped-slot designs.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

Identical or similar components in different figures have the samereference characters.

The illustrations in the figures are diagrammatic and not to scale, butthey may indicate qualitative size relationships.

FIG. 1 shows a perspective view of an exemplary embodiment of amultilayer board 1 according to the invention, comprising a design ofthe sloped slot as a single sloped slot 4 a,5. In this arrangement themultilayer board 1 comprises a core layer 8 that is arranged between thefirst cover layer 2 and the second cover layer 3. The surface normal 12of the multilayer board 1 and thus also for the first cover layer 2,second cover layer 3 and core layer 8 is shown, characterised andfurther clarified by the two right angles on the surface of themultilayer board 1, in the example shown on the first cover layer 2. Thealignment of the direction of transverse extension of the first slopedslot 4 a is arranged in relation to the surface normal 12 at an angle μ.The directions of longitudinal extension of the first sloped slot 4 aand the second sloped slot 5 encompass the angle α 7. Said angle can beas desired; for the sake of simplicity, in FIG. 1 it is essentially 90°.The direction of transverse extension of the second sloped slot 5 alsoruns at an angle relative to the surface normal 12, except that in theembodiment shown the angle is not defined in detail. It is of course notmandatory for the angles of the transverse direction of design of thefirst sloped slot 4 a and the second sloped slot 5 be identical. In thisarrangement the dimensions of the sloped slots in longitudinal directionand in transverse direction essentially depend on the design of the corelayer 8 and furthermore also on the entire multilayer board 1. Thethickness 9 of the sloped slot, in the diagram shown only in relation tothe first sloped slot 4 a, needs to be selected according to the desiredor required mechanical load bearing capacity or deformation, anddepending on the materials. Typical thicknesses 9 of the sloped slotsare, without any limiting interpretation, in the range from below 1 mm,particularly preferred, depending on the board thickness, below 0.5 mmor even essentially below 0.5 mm. By means of such a design of thesloped slot it is then possible with the multilayer board 1 according tothe invention to absorb external forces without having to take intoaccount any far-reaching deformation of the multilayer board 1 andtensile/shear stress loads that occur as a result. Thus the load of therespective cover layer in the transition region is also reduced, andsagging or collapsing of the cover layer 2, in the embodiment shown thefirst cover layer, is effectively prevented. When subjected to externalloads, if a particular limiting force F_(g) is exceeded, the slot isclosed essentially at once, i.e. immediately. In this manner thelimiting force F_(g) can be determined by means of the dimensions anddesign of the multilayer board, and can be matched to the givenrequirements.

FIG. 2 shows a perspective view of a multilayer board 1 according toanother exemplary embodiment of the invention, comprising a slot designof the first sloped slot 4 b as a double sloped slot. The second slopedslot 5 is shown unchanged, but it may also comprise the same or anentirely different slot design. In principle, any desired combination ofdesigns of sloped slots, as shown below in FIGS. 4 a to 4 e, isimaginable. By means of a corresponding design of the first sloped slot4 b as a double sloped slot, changed deformation under load is achieved.This in turn may make changed dimensioning possible.

FIG. 3 a shows a section view of a multilayer panel 1 according toanother exemplary embodiment of the invention, subjected to externalload by the force F in the deformed state with closed sloped slots. Incomparison, FIG. 3 b shows the same multilayer board in its non-deformedstate with open slots. Preferably it should be assumed that the sidecomprising the open sloped slots is the side onto which the force acts.

FIGS. 4 a-e show profile sections comprising various designs of slopedslats. For example, FIG. 4 a shows a single sloped slot; FIG. 4 b adouble sloped slot; FIG. 4 c a Y-shaped sloped slot; FIG. 4 d a multiplesloped slot; and FIG. 4 e a fan-shaped sloped slot. In the case ofseveral angles, e.g. μ₁ and μ₂, in one figure, these angles are notnecessarily identical but they can have the same value. Furtherembodiments are possible, taking into account the scope and nature ofthe invention.

Implementation of the invention is not limited to the above describedexemplary embodiments shown in the figures. Instead, a multitude ofvariants are possible which use the solution shown and the basic ideaaccording to the invention even in the case of fundamentally differentembodiments.

In addition, it should be pointed out that “comprising” does not excludeother elements or steps, and “a” or “one” does not exclude a pluralnumber. Furthermore, it should be pointed out that characteristics orsteps which have been described with reference to one of the aboveexemplary embodiments can also be used in combination with othercharacteristics or steps of other exemplary embodiments described above.Reference characters in the claims are not to be interpreted aslimitations.

LIST OF REFERENCE CHARACTERS

-   1 Multilayer board-   2 First cover layer-   3 Second cover layer-   4 a,b First sloped slot-   5 Second sloped slot-   6 Angle μ-   7 Angle α-   8 Core layer-   9 Thickness of the sloped slot-   10 Position of the cover layer before bending-   11 Position of the cover layer after bending-   12 Surface normal-   F External force

1. A multilayer board for reducing solid-borne sound radiation withimproved mechanical stability when subjected to a load, the multilayerboard comprising: a first cover layer, a second cover layer, and atleast one core layer, wherein the at least one core layer is arrangedbetween the first cover layer and the second cover layer, and whereinthe at least one core layer comprises at least one first sloped slot. 2.The multilayer board of claim 1, wherein the at least one core layerfurther comprises at least one second sloped slot, and whereinrespective longitudinal directions of the at least one first sloped slotand the at least one second sloped slot at a surface of the at least onecore layer are angled with respect to each other at an angle α.
 3. Themultilayer board of claim 2, wherein the angle α is 90°.
 4. Themultilayer board of claim 2, wherein the angle α changes with the courseof the at least one first sloped slot and the at least one second slopedslot.
 5. The multilayer board of claim 1, wherein the first sloped slotis selected from the group consisting of a single sloped slot, a doublesloped slot, a multiple sloped slot, a fan-shaped sloped slot, and aY-shaped sloped slot.
 6. The multilayer board of claim 1, furthercomprising a multitude of core layers.
 7. The multilayer board of claim1, wherein the connection between the first or second cover layer andthe at least one core layer, as well as the connection between two ofthe at least one core layers, is at least in some regions designed as aconnection from the group consisting of an adhesive connection, a solderconnection, a weld connection, a press connection, and a mixturethereof.
 8. The multilayer board of claim 2, wherein the at least onefirst sloped slot or the at least one second sloped slot is designedsuch that when an external force acting on the multilayer board exceedsa particular threshold force, the at least one sloped slot issubstantially closed.
 9. A means of transport comprising at least onemultilayer board of claim
 1. 10. The use of a multilayer board of claim1 in a means of transport.
 11. The multilayer board of claim 1, whereinthe at least one core layer further comprises a first side and a secondside opposite the first side, the at least one first sloped slot beingopen on the first side and not open on the second side.